The present invention relates to a microwave diplexer apparatus and, more particularly, to a microwave diplexer apparatus capable of handling simultaneously two transmitted signals and two received signals in conjunction with a single antenna.
Diplexer apparatus capable of handling simultaneously pairs of transmitted and received signals associated with a single antenna are well known to those skilled in the art. By way of example, diplexer apparatus capable of the above type of operation is disclosed in U.S. Pat. No. 3,731,235, issued May 1, 1973 in the names of Joseph G. DiTullio, Leonard I. Parad and Kenneth E. Story, and also in U.S. Pat. No. 3,731,236, issued May 1, 1973 in the names of Joseph G. DiTullio, Donald J. Sommers and Windsor D. Wright, both of the above patents being assigned to the same assignee as the present application. While the apparatus as described in the abovementioned patents is satisfactory in many communication systems, the apparatus has been used heretofore for the handling of linearly-polarized signals as opposed to circularly-polarized signals. It has further been recognized that it is desirable for any diplexer apparatus, whether employed to handle linearly-polarized or circularly-polarized signals, to have as short an overall length as possible to reduce losses in the apparatus. This reduction in the overall length of a diplexer apparatus has the further advantage of permitting the apparatus to be used in installations where space is at a premium, for example, in installations employing small antennas (e.g., 8-16 meter diameter) as opposed to the more conventional larger antennas (e.g., 32 meter diameter).